Wave-absorbing aerogel for in-situ growth of carbon tube on MXene sheet and preparation method of wave-absorbing aerogel

Abstract

The invention discloses wave-absorbing aerogel for in-situ growth of a carbon tube on an MXene sheet and a preparation method of the wave-absorbing aerogel, and relates to the technical field of microwave absorbing materials, MXene is used as a substrate, cobalt salt, nickel salt, melamine, MXene and Fe2O3 are mixed, then annealing treatment is performed, the cobalt salt and the nickel salt are used as catalysts, and the carbon tube is generated on the MXene nanosheet in situ. Then the compound and deionized water are subjected to ultrasonic mixing, the mixture is put into a mold to be subjected to freeze drying, and the CNT / MXene / Fe2O3 aerogel is obtained. The prepared composite wave-absorbing material is simple in preparation process, impedance matching is optimized while the electromagnetic synergistic effect is enhanced, and the composite wave-absorbing material has potential application prospects in the microwave absorption direction.

Description

Technical Field

[0001] This invention relates to the field of microwave absorbing materials technology, and in particular to a microwave absorbing aerogel in which carbon nanotubes are grown in situ on an MXene sheet and its preparation method. Background Technology

[0002] The rapid development of communication technology, especially the global deployment of sixth-generation networks, has led to the widespread application of electronic devices. However, the operation of these devices generates strong electromagnetic radiation and pollution, which may harm human health and interfere with the stable operation of precision electronic equipment. To address these issues, developing high-performance absorbing materials with wide effective absorption bandwidth (EAB), low reflection loss (RL), and minimal thickness has become a key research focus.

[0003] MXene is a two-dimensional transition metal carbide and nitride with excellent conductivity and tunable surface properties. These properties make it promising for electromagnetic wave absorption. However, its inherent high conductivity and lack of magnetic response often lead to impedance mismatch and low attenuation due to the skin effect. To improve its performance, MXene can be used as a substrate to introduce magnetic components to construct composite materials, thereby adjusting the electromagnetic parameters and enhancing electromagnetic synergy. Furthermore, structural optimization can be performed by introducing heterogeneous interfaces, surface defects, or porous networks to enhance interfacial polarization and dielectric loss, improve impedance matching, and increase microwave absorption capability.

[0004] Carbon nanotubes (CNTs) possess a unique hollow tubular nanostructure and are a typical one-dimensional carbon-based material with high aspect ratio and specific surface area. However, carbon nanotubes exhibit poor dispersibility, are prone to aggregation, and are not conducive to the entry of electromagnetic waves into the material. Therefore, pure carbon nanotube materials still require good impedance matching when used as absorbers. Summary of the Invention

[0005] In order to overcome the above-mentioned problems in the prior art, the present invention proposes a microwave absorbing aerogel for in-situ growth of carbon nanotubes on MXene sheets and its preparation method.

[0006] The technical solution adopted by this invention to solve its technical problem is: a method for preparing a microwave absorbing aerogel with in-situ growth of carbon nanotubes on an MXene sheet, comprising the following steps: Step 1, Preparation of MXene: Ti3AlC2 and LiF powders were added to HCl solution, heated in an oil bath, and the product was washed and sonicated to obtain MXene dispersion. After freeze-drying, MXene nanosheets were obtained. Step 2, Preparation of CNT / MXene / Fe2O3 composite: Cobalt salt, nickel salt, melamine, MXene, and Fe2O3 are dissolved in deionized water to obtain solution A. After stirring evenly, the solution is vacuum dried and then annealed to obtain the CNT / MXene / Fe2O3 composite. Step 3, Preparation of CNT / MXene / Fe2O3 aerogel: The CNT / MXene / Fe2O3 composite prepared in step 2 is mixed with deionized water at different volume ratios and ultrasonicated to obtain a uniform mixed suspension. The suspension is placed in a mold and freeze-dried at low temperature to obtain CNT / MXene / Fe2O3 aerogel.

[0007] The above-mentioned method for preparing a microwave absorbing aerogel with in-situ carbon nanotube growth on MXene sheets includes the following steps: in step 1, the mass of Ti3AlC2 powder and LiF powder is 1g each; the HCl solution is 15mL; the oil bath temperature is 40℃; and the time is 48h.

[0008] In the above-mentioned method for preparing a microwave absorbing aerogel by in-situ growth of carbon nanotubes on an MXene sheet, the washing step 1 involves multiple centrifugations with deionized water until the supernatant is neutral.

[0009] In the above-mentioned method for preparing a microwave absorbing aerogel by in-situ growth of carbon nanotubes on an MXene sheet, the cobalt salt and nickel salt in step 2 are Co(NO3)·6H2O and Ni(NO3)·6H2O, respectively.

[0010] In the above-mentioned method for preparing a microwave absorbing aerogel in which carbon nanotubes are grown in situ on an MXene sheet, the mass ratio of the total mass of cobalt salt and nickel salt, melamine, MXene, and Fe2O3 in step 2 is 80:300:80:1.

[0011] In the above-mentioned method for preparing a microwave absorbing aerogel by in-situ growth of carbon nanotubes on an MXene sheet, during the annealing process in step 2, the heating rate is 5-10℃ / min; the annealing temperature is 700℃; the annealing time is 2h; and the annealing atmosphere is nitrogen or argon.

[0012] In the above-mentioned method for preparing a microwave absorbing aerogel by in-situ growth of carbon nanotubes on an MXene sheet, the freeze-drying in step 3 is performed by unidirectional freeze-drying under the action of liquid nitrogen.

[0013] In the above-mentioned method for preparing a microwave absorbing aerogel by in-situ growth of carbon nanotubes on an MXene sheet, the freezing temperature in step 3 is -58~-62℃ and the freezing time is 40-48h.

[0014] A microwave absorbing aerogel in which carbon nanotubes are grown in situ on an MXene sheet is prepared using the above-described method for preparing a microwave absorbing aerogel in which carbon nanotubes are grown in situ on an MXene sheet.

[0015] The beneficial effects of this invention are that it employs an in-situ growth method, using cobalt and nickel salts as metal catalysts, to grow carbon nanotubes in situ within MXene sheets, constructing a stable and continuous conductive network that balances conductivity loss and impedance matching. After the ice template is constructed, a three-dimensional conductive network is formed inside the MXene aerogel, increasing microwave absorption performance.

[0016] This invention introduces iron oxide, which, under heat treatment conditions, preferentially reduces to metallic iron and undergoes an alloying reaction with cobalt and nickel to form structurally stable cobalt-iron alloys and iron-nickel alloys, thereby enhancing electromagnetic synergy and optimizing impedance matching.

[0017] The CNT / MXene / Fe2O3 aerogel prepared by this invention has a simple preparation method, high reproducibility, and easy-to-control reaction process, exhibiting excellent microwave absorption performance. It shows potential application prospects in the field of microwave absorption. Attached Figure Description

[0018] Figure 1 yes Figure 1 The images show SEM images of MXene, CNCMF-3, and CNCMFA-3; where (a) is the SEM image of MXene, (b) is the SEM image of CNCMF-3, and (c) is the SEM image of CNCMFA-3. Figure 1 (d) is the SEM of CNCMFA-3. Figure 2 ; Figure 2 The images are TEM images of MXene and CNCMF-3; where (a) is the TEM image of MXene and (b) is the TEM image of CNCMF-3. Figure 3 EDS plot for CNCMFA-3; Figure 4 The XRD spectra of the samples prepared in Examples 1 to 5 are shown; where (a) is the XRD spectrum of Ti3AlC2 and MXene, and (b) is the XRD spectrum of NCMF, CNCMF and CCMF. Figure 5 FT-IR plots of MXene, NCMF, CNCMF, and CCMF; Figure 6 Raman plots for MXene, NCMF, CNCMF, and CCMF; Figure 7 The diagram shows the absorption performance of the NCMFA; where (a) is a 3D performance waterfall plot, (b) is the corresponding 2D contour plot, and (c) is a 2D reflection loss plot. Figure 8The diagram shows the absorption performance of CCMFA; where (a) is a 3D performance waterfall plot, (b) is the corresponding 2D contour plot, and (c) is a 2D reflection loss plot. Figure 9 The diagram shows the absorption performance of CNCMFA-1; where (a) is a 3D performance waterfall plot, (b) is the corresponding 2D contour plot, and (c) is a 2D reflection loss plot. Figure 10 The diagram shows the absorption performance of CNCMFA-2; where (a) is a 3D performance waterfall plot, (b) is the corresponding 2D contour plot, and (c) is a 2D reflection loss plot. Figure 11 The diagram shows the absorption performance of CNCMFA-3; (a) is a 3D performance waterfall plot, (b) is the corresponding 2D contour plot, and (c) is a 2D reflection loss plot. Detailed Implementation

[0019] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] Example 1 Step 1, Preparation of MXene: 4g LiF was uniformly dissolved in 60mL HCl (37% by mass) and magnetically stirred for 5min. Then, 4g Ti3AlC2(MAX) was slowly added, and the mixture was stirred in an oil bath at 40℃ for 48h. The mixture was washed with deionized water until the pH reached neutral. Then, it was sonicated under ice water for 3h, and finally centrifuged at 3500rpm for 15min to obtain Ti3C2T. x The MXene nanosheet dispersion was freeze-dried to obtain MXene nanosheets.

[0021] Step 2, Preparation of CNT / MXene / Fe2O3 composite: 0.4 g Ni(NO3)3·6H2O, 1.5 g melamine, 0.4 g MXene, and 0.05 g Fe2O3 were dissolved in 30 mL deionized water and stirred for 24 h to obtain solution A. The product was washed three times with deionized water and dried in a vacuum oven at 60°C for 20 h to obtain a solid. The solid was ground into powder, placed in a tube furnace, and annealed at 700°C under a nitrogen atmosphere at a heating rate of 5°C / min for 2 hours. The sample was named NCMF.

[0022] Step 3, Preparation of CNT / MXene / Fe2O3 aerogel: 0.2 g of sample was placed in 10 mL of deionized water and sonicated for 5 h to obtain a homogeneous suspension. The mixed suspension was poured into a specially made polytetrafluoroethylene mold with a copper column base plate and subjected to unidirectional cryogenic casting under liquid nitrogen. Subsequently, the aerogel was freeze-dried at -60°C and 3 Pa for 48 hours, and the sample was named NCMFA.

[0023] Example 2 Replace 0.4g Ni(NO3)3·6H2O in step 2 with 0.4g Co(NO3)3·6H2O, and perform the same other operations as in Example 1. The resulting complex is named CCMF, and the aerogel is named CCMFA.

[0024] Example 3 In step 2, replace 0.4g Ni(NO3)3·6H2O with 0.27g Ni(NO3)3·6H2O and 0.13g Co(NO3)3·6H2O, and perform the other operations as in Example 1. The resulting complex is named CNCMF-1, and the aerogel is named CNCMFA-1.

[0025] Example 4 Replace 0.4g Ni(NO3)3·6H2O in step 2 with 0.2g Ni(NO3)3·6H2O and 0.2g Co(NO3)3·6H2O, and perform the other operations as in Example 1. The resulting complex is named CNCMF-2, and the aerogel is named CNCMFA-2.

[0026] Example 5 In step 2, replace 0.4g Ni(NO3)3·6H2O with 0.13g Ni(NO3)3·6H2O and 0.27g Co(NO3)3·6H2O, and perform the other operations as in Example 1. The resulting complex is named CNCMF-3, and the aerogel is named CNCMFA-3.

[0027] The samples obtained in Examples 1-5 above were characterized using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, and network vector analysis. Specific test results are as follows: Figures 1-11 As shown.

[0028] Figure 1 SEM images of MXene, CNCMF-3, and CNCMFA-3 are shown. MXene exhibits a typical accordion-like structure, confirming that the Al layer has been successfully removed. Figure 1 a). Introducing Co onto MXene nanosheets 2+ / Ni 2+After melamine and Fe2O3, entangled CNTs and CoFe, FeNi nanoalloys are uniformly and densely distributed on the surface and between the layers of MXene. Figure 1 b). This aerogel exhibits a regular porous structure parallel to the pore arrangement direction, while showing oriented tubular wall structures perpendicular to the pore arrangement direction. Figure 1 cd).

[0029] Figure 2 TEM images of MXene and CNCMF-3. The images show that the MXene nanosheets are very thin. Figure 2 a). After annealing, a large number of interwoven dendritic carbon nanotubes grow on the lamellar MXene. Figure 2 b).

[0030] Figure 3 This is the EDS diagram of CNCMFA-3. The diagram shows that the C, Ti, O, Fe, Co, and Ni elements are relatively evenly distributed in the aerogel.

[0031] Figure 4 The XRD patterns of the samples prepared in Examples 1-5 are shown in the figures. As can be seen from the figures, after etching and exfoliation of Ti3AlC2, MXene is obtained. The diffraction peak shifts to the left from 9.5° to 6.8°, and the peak shape broadens significantly, indicating that Li+ insertion leads to an increase in interlayer spacing, and the Al layer is successfully removed. For the NCMF and CCMF samples, diffraction peaks corresponding to the (110), (101), (200), (111), (210), (211), (220), (310), and (301) crystal planes of rutile TiO2 (PDF#21-1276, P42 / mnm) can be observed. For the CNCMF sample, diffraction peaks corresponding to the (111), (200), (220), and (311) crystal planes of TiO (PDF#08-0117Fm-3m) can be observed. This confirms that MXene undergoes partial oxidation during annealing.

[0032] Figure 5 FT-IR spectra of MXene, NCMF, CNCMF, and CCMF obtained in Examples 1-5 were prepared. (The image was taken at 570 cm⁻¹.) -1 The presence of characteristic Ti–O vibration peaks confirms that TiO2 was annealed. x The existence of [something]. At 1631cm -1 The presence of characteristic C=O vibrational peaks at approximately 2850–2950 cm⁻¹ confirms the presence of carbon derivatives. -1 The weak absorption peak observed at 3440 cm⁻¹ is attributed to C–H stretching vibrations, which are typically associated with residual hydrocarbon groups and defect-related C–H bonds in carbon materials such as carbon nanotubes and MXene. Furthermore, the peak at 3440 cm⁻¹... -1The peak at that point corresponds to the -OH stretching vibration, confirming the presence of hydroxyl groups and adsorbed water molecules.

[0033] Figure 6 Raman plots of MXene, NCMF, CNCMF, and CCMF prepared in Examples 1-5 are shown. The plots show that the etched MXene at 385 cm⁻¹... -1 and 620cm -1 The characteristic peaks are in-plane vibrations of Ti, C, and the surface group. Furthermore, after MXene preparation, the ID / IG ratio decreased from 0.96 to 0.83, indicating an increased degree of graphitization. Calcination further increased the degree of material defects and disorder, which is conducive to the generation of more polarization centers.

[0034] The microwave absorption performance diagrams of the NCMFA, CNCMFA-1, CNCMFA-2, CNCMFA-3, and CCMFA prepared in Examples 1-5 are shown below. Figure 7-11 As shown in the figure, the RL value of NCMFA is always greater than -10dB, indicating almost no microwave absorption performance. Figure 7 The CCMFA achieves an RL value of -17.7 dB at 16.16 GHz (1.5 mm) and an effective bandwidth of 4.48 GHz. Figure 8 The introduction of CoNi co-catalysis significantly improves the microwave absorption performance of CNCMFA. CNCMFA-1 achieves an RL value of -22.57 dB at 16.4 GHz (5 mm) and an effective bandwidth of 1.92 GHz. Figure 9 CNCMFA-2 achieves an RL value of -41.04 dB at 12.56 GHz (2.0 mm) with an effective bandwidth of 4.08 GHz. Figure 10 The CNCMFA-3 exhibits a high RL value of -62.95 dB at 15.2 GHz (1.7 mm), and its bandwidth is also significantly improved to 5.44 GHz. Figure 11 This indicates that carbon nanotubes grown using cobalt-nickel catalysts have richer defect structures and heterogeneous interfaces, resulting in better impedance matching.

[0035] This embodiment discloses a CNT / MXene / Fe2O3 aerogel and its preparation method. Cobalt-nickel salt and iron oxide generate magnetic nanoalloys during the catalytic process, which helps increase magnetic loss and electromagnetic synergistic effects. This is expected to enhance interfacial polarization, impedance matching, and improve electromagnetic wave absorption performance. The preparation method is simple and convenient, and the resulting composite material exhibits strong attenuation capability and good impedance matching with relatively low matching thickness and loading, demonstrating excellent microwave absorption performance.

[0036] The above embodiments are merely exemplary embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art can make various modifications or equivalent substitutions to the present invention within its scope and spirit, and such modifications or equivalent substitutions should also be considered to fall within the scope of protection of the present invention.

Claims

1. A method for preparing a microwave absorbing aerogel by in-situ growth of carbon nanotubes on an MXene sheet, characterized in that, Includes the following steps: Step 1, Preparation of MXene: Ti3AlC2 and LiF powders were added to HCl solution, heated in an oil bath, and the product was washed and sonicated to obtain MXene dispersion. After freeze-drying, MXene nanosheets were obtained. Step 2, Preparation of CNT / MXene / Fe2O3 composite: Cobalt salt, nickel salt, melamine, MXene, and Fe2O3 are dissolved in deionized water to obtain solution A. After stirring evenly, the solution is vacuum dried and then annealed to obtain the CNT / MXene / Fe2O3 composite. Step 3, Preparation of CNT / MXene / Fe2O3 aerogel: The CNT / MXene / Fe2O3 composite prepared in step 2 is mixed with deionized water at different volume ratios and ultrasonicated to obtain a uniform mixed suspension. The suspension is placed in a mold and freeze-dried at low temperature to obtain CNT / MXene / Fe2O3 aerogel.

2. The method for preparing a microwave absorbing aerogel with in-situ carbon nanotube growth on an MXene sheet according to claim 1, characterized in that, In step 1, the mass of both Ti3AlC2 powder and LiF powder was 1g; the HCl solution was 15mL; the oil bath temperature was 40℃; and the time was 48h.

3. The method for preparing a microwave absorbing aerogel with in-situ carbon nanotube growth on an MXene sheet according to claim 1, characterized in that, The washing process in step 1 involves multiple centrifugations with deionized water until the supernatant is neutral.

4. The method for preparing a microwave absorbing aerogel with in-situ carbon nanotube growth on an MXene sheet according to claim 2, characterized in that, The cobalt salt and nickel salt in step 2 are Co(NO3)·6H2O and Ni(NO3)·6H2O, respectively.

5. The method for preparing a microwave absorbing aerogel with in-situ carbon nanotube growth on an MXene sheet according to claim 4, characterized in that, In step 2, the total mass of cobalt and nickel salts, melamine, MXene, and Fe2O3 are in a mass ratio of 80:300:80:

1.

6. The method for preparing a microwave absorbing aerogel with in-situ carbon nanotube growth on an MXene sheet according to claim 5, characterized in that, During the annealing process in step 2, the heating rate is 5-10℃ / min; the annealing temperature is 700℃; the annealing time is 2h; and the annealing atmosphere is nitrogen or argon.

7. The method for preparing a microwave absorbing aerogel with in-situ carbon nanotube growth on an MXene sheet according to claim 1, characterized in that, The freeze-drying in step 3 is a unidirectional freeze-drying process performed under the action of liquid nitrogen.

8. The method for preparing a microwave absorbing aerogel with in-situ carbon nanotube growth on an MXene sheet according to claim 7, characterized in that, The freezing temperature in step 3 is -58~-62℃, and the freezing time is 40-48h.

9. A microwave-absorbing aerogel in which carbon nanotubes are grown in situ on an MXene sheet, characterized in that, The microwave absorbing aerogel is prepared by the method described in any one of claims 1-8, which involves in-situ growth of carbon nanotubes on an MXene sheet.

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